Photovoltaic Roofing Components and Systems

ABSTRACT

The present invention relates particularly to photovoltaic roofing systems in which photovoltaic elements are integrated on a roof deck with conventional roofing materials. In one aspect, a photovoltaic roofing system includes a two-part tee element disposed on a roof deck, the two-part tee element comprising a base piece including a central portion; two opposed horizontally-extending first and second flanges extending from the central portion, and a top piece attachment feature formed in the central portion, and a top piece including a base piece attachment feature mated with the top piece attachment feature of the base piece; and a vertically extending portion extending from the base piece attachment feature. A first photovoltaic element can be disposed on the roof adjacent the base piece with its edge disposed on the horizontally-extending first flange of the base piece of the two-part tee element.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/675,568, filed Nov. 13, 2012, which claims the benefit ofpriority to U.S. Provisional Patent Application Ser. No. 61/559,593,filed Nov. 14, 2011, each of which is hereby incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to photovoltaic systems. Thepresent invention relates more particularly to photovoltaic roofingsystems in which photovoltaic elements are integrated on a roof deckwith conventional roofing materials.

2. Summary of the Related Art

The search for alternative sources of energy has been motivated by atleast two factors. First, fossil fuels have become increasinglyexpensive due to increasing scarcity and unrest in areas rich inpetroleum deposits. Second, there exists overwhelming concern about theeffects of the combustion of fossil fuels on the environment due tofactors such as air pollution (from NO_(x), hydrocarbons and ozone) andglobal warming (from CO₂). In recent years, research and developmentattention has focused on harvesting energy from natural environmentalsources such as wind, flowing water, and the sun. Of the three, the sunappears to be the most widely useful energy source across thecontinental United States; most locales get enough sunshine to makesolar energy feasible.

Accordingly, there are now available components that convert lightenergy into electrical energy. Such “photovoltaic cells” are often madefrom semiconductor-type materials such as doped silicon in either singlecrystalline, polycrystalline, or amorphous form. The use of photovoltaiccells on roofs is becoming increasingly common, especially as deviceperformance has improved. They can be used to provide at least asignificant fraction of the electrical energy needed for a building'soverall function; or they can be used to power one or more particulardevices, such as exterior lighting systems.

Accordingly, research and development attention has turned toward thedevelopment of photovoltaic products that are adapted to be installed ona roof. While photovoltaic elements have been in use for some time, theytend to be heavy and bulky, and aesthetically unfavorable when installedon a roof. Roofing products having photovoltaic cells integrated withroofing products such as shingles, shakes or tiles have been proposed. Aplurality of such photovoltaic roofing elements (i.e., includingphotovoltaic media integrated with a roofing product) can be installedtogether on a roof, and electrically interconnected to form aphotovoltaic roofing system that provides both environmental protectionand photovoltaic power generation. These can be very advantageous, butcan be difficult to install on steep surfaces, and can often result inincomplete coverage of the roof surface with photovoltaic powergeneration. Moreover, fabrication and installation and connection of aplurality of smaller photovoltaic roofing elements can in somecircumstances be a very slow, tedious, and costly process. There remainsa need for improved devices and methods for the integration ofphotovoltaic media onto roof decks together with conventional roofingmaterials.

SUMMARY OF THE INVENTION

One aspect of the present invention is a photovoltaic roofing system foruse on a roof deck, the photovoltaic roofing system comprising:

-   -   a two-part tee element disposed on a roof deck, the two-part tee        element comprising:        -   a base piece including a central portion; two opposed            horizontally-extending first and second flanges extending            from the central portion, and a top piece attachment feature            formed in the central portion, and        -   a top piece including a base piece attachment feature mated            with the top piece attachment feature of the base piece; and            a vertically extending portion extending from the base piece            attachment feature; and    -   a first photovoltaic element disposed on the roof adjacent the        base piece, the first photovoltaic element having its edge        disposed on the horizontally-extending first flange of the base        piece of the two-part tee element.

Another aspect of the invention is a method for installing aphotovoltaic roofing system as described above on a roof, the methodcomprising:

-   -   affixing one or more base pieces to a roof;    -   disposing one or more photovoltaic elements on the roof, each        adjacent a base pieces, such that horizontal edges of the        photovoltaic elements are each disposed on a flange of a base        piece; and    -   assembling a top piece with each base piece to form the two-part        tee elements.

The photovoltaic roofing components and systems of the present inventioncan result in a number of advantages over prior art photovoltaicsystems. In certain aspects, the present invention addresses the problemof framing of roofing integrated photovoltaic systems on a roof. Forexample, in one embodiment, the present invention provides plastic orpolymeric parts, which are non-conductive and do not require electricalgrounding when they are a part of a photovoltaic system. Moreover,corrosion can be avoided by the use of plastic or polymeric parts. Incertain embodiments, the present invention provides a two-part “tee” orframing piece, which can allow for easy replacement of damaged parts,and can allow for changes in shape and color as desired to adapt thevisual aspect of the array. In certain embodiments, a flange can beincluded to assist in holding down a photovoltaic element onto a roofsurface. A two-part configuration also allows the selective use of morecostly weather-durable materials in the parts of the framing that areexposed to the elements (e.g., the top pieces). Further, in certainembodiments a common base piece can be used for both tee pieces and sideframing pieces, with different components being fitted with differingtop pieces (e.g., at the time of installation). Other advantages willbecome apparent to the person of skill in the art in view of the presentdisclosure.

The accompanying drawings are not necessarily to scale, and sizes ofvarious elements may be distorted for clarity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top perspective view of a photovoltaic roofingsystem on a roof.

FIG. 2A is a partial cross-sectional schematic view of the side flashingof the embodiment of FIG. 1.

FIG. 2B is a partial cross-sectional view of another embodiment of aside flashing.

FIG. 3A is an exploded cross-sectional schematic view of components of aphotovoltaic element including a two-part tee element and twophotovoltaic elements.

FIG. 3B is a cross-sectional schematic view of the components of FIG.3A, as assembled in a photovoltaic system.

FIG. 4A is a perspective schematic view of the components of FIG. 3A.

FIG. 4B is a perspective schematic view of the assembly of FIG. 3B.

FIG. 5A is an exploded cross-sectional schematic view; and FIG. 5B is across-sectional schematic view of a photovoltaic roofing system using adifferent two-part tee element, according to another embodiment of theinvention.

FIG. 6 is a cross-sectional schematic view of a base piece comprising aplurality of materials.

FIG. 7 is a cross-sectional schematic view of three embodiments of toppieces of tee elements, each comprising a plurality of materials.

FIG. 8 is an exploded cross-sectional schematic view of a two-part teeelement according to one embodiment of the invention.

FIG. 9A is an exploded cross-sectional schematic view, and FIG. 9B is anassembled cross-sectional view of a two-part tee element. according toanother embodiment of the invention.

FIG. 10A is an exploded cross-sectional schematic view, and FIG. 10B isan assembled cross-sectional view of a two-part tee element and afastener. according to another embodiment of the invention.

FIGS. 11, 12, and 13 are cross-sectional views of other two-part teeelements and assemblies according to other embodiments of the invention.

FIG. 14 is a cross-sectional view of a base piece of a two-part teeelement according to another embodiment of the invention.

FIG. 15 is a cross-sectional view of a two-part tee element usedsuitable for use as a side flashing element and an assembly thereofincluding a roofing material and a photovoltaic element, according toone embodiment of the invention.

FIG. 16 is a perspective view of an assembly of components including anend cap according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides a two-part tee element(i.e., usable as a framing piece) for a roofing integrated photovoltaicsystem. The two-part tee element includes a base piece (e.g., in stripform); and a top piece (e.g., in strip form). In one aspect, a basepiece includes two opposed horizontally-extending first and secondflanges extending from a central portion. A first photovoltaic elementcan be disposed on the roof adjacent to the base piece, with its edgedisposed on the horizontally-extending first flange. Desirably, thephotovoltaic element overlaps the first flange by at least about oneinch. A second photovoltaic element or a roofing element can be disposedon the roof adjacent the base piece opposite the first photovoltaicelement, with its edge disposed on the horizontally-extending secondflange. Desirably, the second photovoltaic element or the roofingelement overlaps the second flange by at least about one inch. A toppiece attachment feature (e.g., a receiver channel) is provided in thecentral portion of the base piece. The two-part tee element alsoincludes a top piece, which includes a base piece attachment featureconfigured to mate with the top piece attachment feature of the basepiece; and a vertically extending portion extending from the base pieceattachment feature. For example, the top piece can include a verticalleg that is inserted into a receiver channel in the base piece. Wheninstalled, the top piece can delineate regions separating photovoltaicelements one from another and/or from fields of conventional roofingmaterials mounted on a roof.

In certain embodiments, covering flanges extend outwardly from the sidesof the top piece that can overlap the top surface of an adjacentphotovoltaic element or roofing element. For example, in one embodiment,the top piece further includes a first covering flange extendingoutwardly from a side of the top piece, and overlapping the top surfaceof the first photovoltaic roofing element, the second photovoltaicelement, or a roofing element. In certain such embodiments, a secondcovering flange extends outwardly from the opposite side of the toppiece, and overlaps the top surface of the first photovoltaic element,the second photovoltaic element, or a roofing element.

In one embodiment of the invention, a base piece has a receiver channeland side flanges. Fasteners are applied through the base piece withinthe receiver channel for attachment to a roof. A photovoltaic element isattached to the roof adjacent to the base piece, at least partiallycovering one of the side flanges. The receiver channel provided in thebase piece is configured to accept a mating structure from a top piece.As described above, the top piece can to delineate regions separatingphotovoltaic elements one from another and/or from fields ofconventional roofing materials mounted on the roof. In certainembodiments, a covering flange extends outwardly and downwardly from thetop piece and can engage the top surface of the adjacent photovoltaicelement.

The top piece can include a variety of physical structures or shapes. Incertain embodiments, it provides a vertically-extending strip todelineate portions of the photovoltaic array. Shadows cast by thevertical strip can visually break up the field of blue (or other colorof the photovoltaic materials) to make the system appear more consistentwith other roofing materials.

In another embodiment, one or more covering flanges can extend from thetop piece (e.g., a vertically-extending portion thereof) to engage aphotovoltaic element disposed on a horizontally-extending flange of thebase piece. This engagement can assist in mechanically affixing thephotovoltaic element to the roof surface as a supplement to an adhesiveor other attachment system. The covering flange can prevent edge upliftof the photovoltaic element from the roof deck. They can also reduce thepossibility of moisture, dirt, insects, leaves, ice & snow, or othermatter intruding under the photovoltaic element that could lead todisbondment from the surface.

In another embodiment, a covering flange can cover and flash in the edgeof a shingle field adjacent the photovoltaic elements on the roof.

Another aspect of the invention is a method for installing aphotovoltaic roofing system on a roof. The method includes affixing oneor more base pieces (as described herein) to a roof deck. The person ofskill in the art can provide sufficient spacing between base pieces toallow photovoltaic elements to fit between the top piece attachmentfeatures (e.g., receiver channels). One or more photovoltaic elementsare then disposed on the roof, each adjacent a base piece, such thathorizontal edges of the photovoltaic elements are each disposed on aflange of a base piece. After disposal of the photovoltaic elements, toppieces are assembled with the base pieces to form two-part tee elements.In certain embodiments, each top piece includes a flange extendingoutwardly therefrom, covering an edge of a photovoltaic element disposedon a flange of the base piece.

In certain embodiments of the methods described herein, one of the basepieces is disposed at a side edge of the field of the array ofphotovoltaic elements, near a field of roofing material. The top piecethat is attached to (e.g., inserted into the channel of) the side edgebase piece has a flange extending outwardly from the direction of thephotovoltaic array, which provides a flashing aspect to merge thephotovoltaic roofing system with the field of roofing material (e.g.,shingles).

Having two-part tees and other framing pieces has an advantage ininstallation of photovoltaic roofing systems. The lower profile of thebase piece with the top piece attachment feature (e.g., receiverchannel) provides assistance and acts as a guide in placement andalignment of photovoltaic elements on the roof, and does not protrudevery high from the roof surface. This helps in avoiding damage toframing pieces while installation is in progress and avoids workerstripping over the framing pieces, potentially damaging the frame piecesor the photovoltaic element. Installation of the top piece provides afinished look to the system, and in certain embodiments can provide theinterfaces between materials with additional protection from ingress ofwater.

A photovoltaic roofing system is shown in schematic top perspective viewin FIG. 1. Photovoltaic roofing system 100 includes a roof deck 110,upon which one or more (in this case, three) photovoltaic elements 120are disposed. The one or more photovoltaic elements (together) have atop edge 122 facing the upper end of the roof deck; a bottom edge 124facing the lower end of the roof deck, and two side edges 126. Thephotovoltaic roofing system also includes a plurality of roofingelements 130 disposed outside the photovoltaic area, along their sideedges 126. In this embodiment, the roofing elements are granule-coatedbituminous shingles. Of course, other types of roofing elements can beused with the photovoltaic roofing system. In order to provide a desiredoverlap pattern of the roofing elements, it may be necessary to cutcertain of the roofing elements (e.g., roofing elements 130 a) orotherwise provide roofing elements of different widths. Photovoltaicroofing system 100 also includes linearly-extending side flashingtwo-piece tee elements 140 disposed along the side edges of thecontiguously-disposed photovoltaic elements and linearly-extendingbatten two-piece tee elements 141 disposed between the photovoltaicelements. Similar roofing systems are described in more detail in U.S.Patent Application Publications nos. 2010/0242381 and U.S. patentapplication Ser. No. 13/243,726, each of which is hereby incorporatedherein by reference in its entirety. As the person of skill in the artwill appreciate in view of the present disclosure, the two-piece teeelements described herein can be used as any of the side flashing or teeelements described in the above-referenced applications (e.g., as items140 and 141 in FIG. 1). The present disclosure specifically contemplateseach embodiment described in the above-referenced applications, with anyof the two-piece tee elements described herein used as any side flashing(separating photovoltaic elements from roofing elements) or tee elements(separating adjacent photovoltaic elements) configured therein.

The side flashing two-piece tee element of the embodiment of FIG. 1 isshown in more detail in the partial schematic cross-sectional view ofFIG. 2A. The side flashing two-piece tee element 140 has across-sectional shape including a base piece 142 having flanges 144, 146extending therefrom. The base piece 142 also includes a top pieceattachment feature (the upwardly-pointing triangular feature). The sideflashing two-piece tee element 140 also includes a top piece 147, whichextends vertically from the base piece, and includes a base pieceattachment feature (here, a triangular channel) which mates with toppiece attachment feature of the base piece. The flange 146 facing thecontiguously-disposed photovoltaic elements is at least partiallydisposed between the photovoltaic element 120 and roof deck 110. Theflange 144 facing away from the contiguously-disposed photovoltaicelements is at least partially disposed between the roofing element 130and roof deck 110. The side flashing two-piece tee element can therebyprovide a water resistant seam between the contiguously-disposedphotovoltaic elements and the roofing elements. Linearly extendingtwo-piece tee elements 141 are similar in construction and similarlyinstalled (not shown), but have the flanges 144 and 146 are each atleast partially disposed between photovoltaic elements 120 and the roofdeck 110.

The photovoltaic roofing systems described herein can provide a numberof advantages over conventional photovoltaic installations. For example,when using traditional photovoltaic panels, bolts must be driven throughthe roof (and through the roofing elements protecting the roof) in orderto hold the panels in place, which can create the potential for leakage.In many cases, the bolts must be driven through the framing members ofthe roof, in order to provide sufficient anchoring for the relativelyheavy photovoltaic panels. In certain embodiments of the presentphotovoltaic roofing system, there is no need for bolts through theroof, or through any roofing elements. Fasteners are often used to holdthe two-piece tee elements in place, but such fasteners can be coveredby the roofing elements and photovoltaic elements disposed on theflashing. Alternatively, two-piece tee elements can be fastened usingfasteners that go through a central portion of a base piece that iscovered by a top piece of the two-piece tee element. Accordingly, in oneembodiment of the invention, all fasteners holding the components of thephotovoltaic roofing system in place are covered by roofing elements orphotovoltaic elements, or by a top piece of a two-piece tee element.Moreover, roof penetrations for electrical connections can be minimizedwith respect to conventional systems.

An alternative side flashing two-piece tee element 143 is shown in FIG.2B. The side flashing two-piece tee element 143 has a cross-sectionalshape including a base piece 142 as described above with reference toFIG. 2A. The side flashing two-piece tee element 143 also include a toppiece 148, which extends vertically from the base piece. The top piece148 is generally as described above with respect to FIG. 2A, but alsoincludes a sidewardly directed flange 149 extending from itsvertically-extending feature (here, at the top). The flange 146 facingthe contiguously-disposed photovoltaic elements is at least partiallydisposed between the photovoltaic element 120 and roof deck 110. Theflange 144 facing away from the contiguously-disposed photovoltaicelements is at least partially disposed between the roofing element 130and roof deck 110. The flange sidewardly directed flange 149 extends tocover at least a portion of the edge of the roofing element 130. Theside flashing can thereby provide a water resistant seam between thecontiguously-disposed photovoltaic elements and the roofing elements.Sidewardly directed flanges can similarly be used to cover the interfaceof a photovoltaic element with a base piece flange.

FIGS. 3A, 3B, 4A and 4B show another embodiment of the two-part tee ofthe invention having a top piece 241 with an upwardly extending portion242; and a base piece 240. The base piece 240 has a receiver portion 247with a receiver 248 to receive a snap-fitting bayonet 245 from top piece241. The top piece has side flanges 243 that extend to cover the edgesof photovoltaic elements 220 when assembled on a roof 250. In oneembodiment, the top piece is slidably engaged with the base piece. Inanother embodiment, the cap piece is rigidly held by the base piece. InFIGS. 3B and 4B, the photovoltaic elements are rigid, and do not followthe slope of the flanges of the base piece. In other embodiments, thephotovoltaic elements can follow the slope of the flanges (e.g., theyare flexible; or have a downward-facing surface adapted to receive thesloped flange).

FIGS. 5A and 5B show a two-part tee element having an alternative toppiece 341 having an upwardly extending portion 342 and a bayonet-likefastener 345 for attachment to base piece 240. In this embodiment theupwardly extending portion does not include side flanges to cover theedges of photovoltaic elements 220 when assembled (as shown in FIG. 5B).

In FIG. 6, a base piece 440 is made up of at least two differentmaterials, the central portion 450 having a different composition thanthe side flanges 444 and 446. In one aspect the central portion 450 thatis partially exposed to the environment when the base piece is installedon the roof is comprised of more weatherable durable polymeric materialsthan the flanges 444, 446 that are not exposed. In another aspect, forembodiments in which the base piece is attached to the roof withfasteners through the side flanges 444 and 446, the flanges can beconstructed of a material that is softer and readily receptive to nailapplication to a roof deck.

In certain embodiments, the top piece of the two-part tee is formed froma different material than the base piece. Because the two-part tee has atop piece that is exposed and a base piece that is not exposed in use, amore weather resistant material can be used for the top piece and lesscostly materials can make up the base. Three different top pieceembodiments are shown in schematic cross-sectional view in FIG. 7. Toppiece 441 a has a vertically extending portion 442 a and a fasteningportion 445 a (i.e., to act as a base piece attachment feature). A firstmaterial 447 a is used in the upwardly extending portion and fasteningpart of the body of the top piece. The side flanges 443 a are made of amaterial of a different composition 451 a. In one embodiment, materials447 a and 451 a are coextruded to shape the top piece 441 a. In analternative embodiment, side flanges 443 a are inserted into thestructure of the top piece 441 a to yield a top piece having sideflanges differing in composition from the central body of the piece. Inone aspect such a configuration can be useful to provide rubbery orflexible side flanges for sealing against the top surface ofphotovoltaic elements when installed on a roof. In another aspect, theside flanges can be stiffer than the main body of the top piece to helphold the edges of a photovoltaic element in place.

Top piece 441 b has a vertically extending portion 442 b and a fasteningportion 445 b (i.e., to act as a base piece attachment feature). A firstmaterial 447 b is used in the core of the upwardly extending portion andfastening part of the body of the top piece. The vertically extendingportion 442 b and the side flanges 443 b are covered by a capstock of amaterial of a different composition 448 b. In one embodiment, materials447 b and 448 b are coextruded to shape the top piece 441 b. Thecoextrusion provides a weatherable cap on the exposed portions of thetop piece. The core can be formulated for economic advantage without asgreat a need to account for weatherability concerns, and be formulatedto economic advantage in tailoring physical and mechanical propertiesfor the bulk of the top piece.

Top piece 441 c has a vertically extending portion 442 c and a fasteningportion 445 c (i.e., to act as a base piece attachment feature). A firstmaterial 447 c is used in the core of the upwardly extending portion andfastening part of the body of the top piece. The vertically extendingportion 442 c and the side flanges 443 c are covered by a capstock of amaterial of a different composition 448 c. A third composition 449 c isinterposed between the core material 447 c and the capstock 448 c. Inone embodiment, materials 447 c, 448 c and 449 c are coextruded to shapethe top piece 441 c. Coextrusion provides a weatherable cap on theexposed portions of the top piece. In one aspect the capstock 448 c isat least partially transparent in the near infrared and the inner layer449 c is reflective of infrared radiation. The core can be formulatedfor economic advantage without as great a need to account forweatherability concerns, and be formulated to economic advantage intailoring physical and mechanical properties for the bulk of the toppiece. Thus, in one embodiment the top piece is solar reflective andpresents a desirable colored visual aspect to a viewer. The solarreflective aspect enables the part to have less heat buildup on a roofand reduced tendency for heat distortion or other dimensional changes inuse.

FIG. 8 is a cross-sectional view of another two-part tee element havinga top piece 541 and a base piece 540. The top piece has a verticallyextending portion 542, side flanges 543, and a downwardly directedportion 545 for engaging with the base piece (i.e., to serve as a basepiece attachment feature). The downwardly directed portion 545 has twolegs 550 and detent features 551 that engage with corresponding detentfeatures 549 in the opening 548 of the top piece attachment feature 547of the base. The base piece also has two side flanges 544 and 546. Inthis embodiment, the parts have a thinner and more uniform thickness fora profile extrusion with easier polymer flow and cooling with lesspotential for distortion and warpage of parts. In this embodiment, theheight of the top piece from the bottom of the attachment legs to thetop of the upwardly extending portion is about 1 inch. The upwardextension has a thickness of about ⅛ inch. The side flanges for the toppiece extend to cover a width of about 1½ inches.

FIG. 9A is a cross-sectional schematic view of another two-part teeelement having a top piece 571 and a base piece 570, the assembled partsbeing shown in cross-sectional schematic view in FIG. 9B. The top piecehas a vertically extended portion 572, side flanges 573, and adownwardly directed portion 575 that serves as a base piece attachmentfeature. The downwardly directed portion 575 has two legs 580 and detentfeatures 581 that engage with corresponding detent features 579 in theopening 578 of the top piece attachment feature 577 of the base piece.The base piece also has two side flanges 574 and 576. In the embodimentof FIGS. 9A and 9B, the height of the top piece from the bottom of theattachment legs to the top of the upwardly extending portion is about1.2 inches. The upward extension has a thickness of about ⅛ inch. Theside flanges for the top piece extend to cover a width of about 1.58inches. The thickness of the side flanges 573 is about 0.080 inch, as isthe thickness of the wall of the receiver 577. The width at the prongsof the detent feature 581 is about 0.437 inch such that the legs 580flex to provide a retaining force when assembled into the receivingchannel 578 which has a width of about 0.42 inch.

FIGS. 10A and 10B are cross-sectional schematic views of a two-part teeelement similar to that of FIG. 9A, with a photovoltaic element 625 anda fastener 600, and an assembly thereof. In this case, the top piece 571is the same as that in FIG. 9A, but the base piece 610 has a moreflattened bottom (indicated by reference numeral 620) in the region ofthe receiving channel 618 where the fastener 600 penetrates the base toattach it to a roof deck. The base piece has side flanges 614 and 616and the receiver portion 617 includes a detent feature 619 to engagewith the top piece 571. A photovoltaic element 625 is disposed on theflange 614 on the left side of the receiver of the base piece. Thephotovoltaic element 625 has an active area 626 and a non-active area627 near the edge of the module. When the top piece 571 is engaged withbase piece 610 as in the assembly 630, the side flanges 573 engage thenon-active portion of the photovoltaic element and do not encroach onthe active area thereof. As a photovoltaic element is not present on theright side of base piece 610, a gap 631 is shown to represent the spaceto accommodate a module. A distance 632 is provided between the edge ofthe module 625 and the receiver portion 617 on the base piece toaccommodate thermal expansion and contraction of the parts in use.

FIGS. 11, 12, and 13 are cross-sectional schematic views of othertwo-part tee elements and assemblies. In FIG. 11, the top piece 671 hasdeformable side flanges so that in the assembled state, top piece 671 ahas a side flange 673 re-shaped to conform to and accommodate thephotovoltaic element and engage it with a tension to participate inmaintaining it in position. An alternate shape side flange 674 is alsoshown. The top piece 541 and base piece 540 of FIG. 12 are similar tothose of FIG. 8, but the top piece is deformed to take on another shape681 with shaped flanges 684 to engage the photovoltaic element 625. Thetop piece 741 in FIG. 13 has an alternative shape with a minimalupwardly extending portion 742. As shown here, it is configured toengage with base piece 540. Alternatively, side flanges 784 of top piece781 are shaped to engage the photovoltaic element in a non-active area.The top piece 741,781 has a lower profile with less potential to shadowactive areas of photovoltaic material at grazing illumination angles,yet still shows a delineation of roof texture between adjacentphotovoltaic elements.

FIG. 14 is a cross-sectional view of an alternative base piece 840having a flat bottom in the fastening zone 820 and an angled ribstructure 821 to provide an angled surface to mate with the beveledshape of a fastener such as a screw head.

FIG. 15 is a cross-sectional schematic view of a two-part side flashingelement and an assembly thereof including a roofing material and aphotovoltaic element. In this case, top piece 941 has a verticallyextending portion 942, a side flange 943, and an extended side flashingflange 945. The top piece engages with base piece 540 at the left sideof a photovoltaic array. When assembled, the side flashing flange 945extends over the top surface of shingle 930 or other roofing materialadjacent the photovoltaic array. The shorter side flange engages thenon-active area of the end photovoltaic element. In FIG. 15, flashingtop piece 981 has a flashing 985 covering the edge of the shingle 930 toclose the roof and the shorter flange 983 engaging the non-active area922 of photovoltaic element 920. It will be understood that a flashingfor a left edge of a photovoltaic roofing system can be reversed inorientation to yield a right edge flashing piece. In the case of thisinvention, the same base piece can be used for either the left or rightedge side flashing, as well as for the battens or tee pieces for theinterior portions of the system.

The flashing parts described herein can be made in a number of ways, asthe person of skill in the art will appreciate. For example, flashingparts can be made using coextrusion. With coextrusion, differentsections of the tee can be made from different compositions. Forexample, the flange portions of the various parts could be made from adifferent material than the rest of the body. When the downwardlydirected flanges from an upper part are made from a rubbery material,they can flexibly engage the PV module to provide a seal effect. In someembodiments, when the side flanges of the base piece are made from aflexible material they can accommodate fasteners and allow hard nailingwhile minimizing issues of buckling due to thermal expansion andcontraction or movement of the roof, as the flexible material candissipate or redirect the mechanical stresses. Coextrusion can alsoallow portions of the parts to have solar reflective properties tominimize heat distortion effects, as described in U.S. Pat. No.7,846,548, which is hereby incorporated herein by reference in itsentirety. For example the top exposed piece can be colored by aninfrared-transparent visibly colored layer as a capping layer with anunderlying inner layer that is solar reflective.

Plastic parts can provide more impact resistant performance for the teeor other framing pieces. The polymeric materials are resilient comparedto metal parts, and will preferably not be subject to permanentdeformations by hail, or other impacts, for example.

The two-part tee elements of the invention can result in a variety ofadvantages. For example, having two parts can allow for facilereplacement of the exposed portion. This could be beneficial if a partin the field became damaged. It could also yield a changeable appearancefor the photovoltaic roofing system for the building owner who wouldlike to change the color by replacing tees or frame pieces withdifferently decorated accessories.

Thermal expansion effects can be addressed by the two-part tee elementsdescribed herein. In one instance, the base piece attachment feature ofthe top piece is slidably engaged with the top piece attachment featureof the base piece (which can be formed as one or more tracks or slots).The mechanical slot allows sliding of the parts as they expand orcontract, leaving less chance for heat distortion for lineal sections offraming parts. In certain embodiments, an end cap is provided at thebottom end of the base piece on the roof. The end cap engages the baseand closes the bottom end of the two-piece structure to moisture andother intrusions. It can also provide a mechanical stop and allows forfree movement of the top piece so that in repeated lineal expansion andcontraction, the top piece is retained by the base and does not migratedown the roof. The end cap can be attached by a mechanical fastener suchas a nail or a screw or other mechanical fastener, or by an adhesive. Anexample of an end cap is shown in the partial perspective schematic viewof FIG. 16. The embodiment of FIG. 16 is identical to that of FIG. 4B,but for the addition of the end cap 1690. In some cases, the capprovides a clip structure 1692 for retaining wiring or accessories forthe array, or alternatively for attachment of decorative features to theroof, such as, for example, strings of Christmas lights, or the like. Inone embodiment the end cap comprises a snow guard. In anotherembodiment, a set screw or other mechanical stop (see ref no 490 of FIG.4B) serves to prevent downward movement of the top cover piece below afixed point.

A variety of materials could be used for making the plastic framingparts, for example, PVC, ASA, AES, CPVC, or PP. In some cases,coextrusion is used to make the parts having a substrate layer for thebulk of the part and a capstock layer for exposed portions. Thesubstrate layer is a bulk layer and can be produced from fillerreinforced polymers. Examples of suitable polymers include polyethyleneresin, ethylene-vinyl acetate copolymer resin, polypropylene resin,polystyrene resin, ASA resin, ABS resin, methacrylic resin, PVC resin,polyamide resin, polycarbonate resin, polyethylene terephthalate resin,polybutylene terephthalate resin, diallylphthalate resin, urea resin,melamine resin, xylene resin, phenol resin, unsaturated polyester resin,epoxy resin, furan resin, polybutadiene resin, polyurethane resin,melamine phenol resin, chlorinated polyethylene resin, vinylidenechloride resin, acrylic-vinyl chloride copolymer resin, polyacetalresin, polymethylpentene resin, polyphenylene oxide resin, denatured PPOresin, polyphenylene sulfide resin, butadiene styrene resin, polyaminobismaleimide resin, polysulfone resin, polybutylene resin, siliconeresin, polyethylene tetrafluoride resin, polyethylene fluoride propyleneresin, perfluoro alkoxy fluoride plastic, polyvinylidene fluoride resin,MBS resin, methacrylic-styrene resin, polyimide resin, polyallylateresin, polyallylsulfone resin, polyethersulfone resin,polyetheretherketone resin, chlorinated polyvinyl chloride resin, andthe like. Particularly suitable polymers include PVC, CPVC, C-PE, co-PP,homo-PP, HDPE, UMWPE, LDPE, or combinations thereof. The composition caninclude a filler such as long or short glass fiber, natural mineralfiber, natural fibers, limestone or CaCO₃, talc, mica, wollastonite,wood fiber, wood flour, straw, kenaf, rice hulls, corn stalks, cork, orother fillers. The capstock layer can include polymers such as PMMA,PEMA, ASA, AES, ASA/PVC alloy, PVDF, ABS, polycarbonate, PVC, CPVC, PP,HDPE, UMWPE, LDPE, or other weatherable polymers. The capstock materialscan contain additives such as one or more of UV blockers, UVstabilizers, antimicrobial agents, gloss reduction agents, thermalstabilizers and IR reflective pigments. In some embodiments, polymer orplastics for the substrate or capstock layer can be foamed usingchemical blowing agent or physically blown with gas CO₂ or N₂ usingmicrocellular foaming technology.

The parts described herein can also be formed from fiber reinforcedplastics. For example, the parts could be made by pultrusion to producea uniaxially fiber reinforced plastic lineal piece in eitherthermosetting or thermoplastic materials. Plastisol pultrusion methodsare described in U.S. Patent Application Publication no. 2007/0126142and U.S. Pat. No. 7,987,885, each of which is hereby incorporated hereinby reference in its entirety.

In certain embodiments, flanges engaging photovoltaic elements areformed from ceramic (e.g., covering flanges of the top piece). Insertionof ceramic strips into a plastic base piece allows the use of aweatherable ceramic material that is stiff to hold a photovoltaicelement down. In another alternative, the entire top piece can be madeout of ceramic. The ceramic top strip could be decorated to fit theaesthetic of a ceramic tile roof for a photovoltaic roofing system thatis made to complement a tile roof.

The two-part tee elements described herein can be attached to a roofdeck through their base pieces, in any of a number of ways. As describedabove, fasteners can be used, for example in the central portion of thebase piece. When the base piece includes a channel or a slot as part ofthe top piece attachment feature, mechanical fasteners can be installedthe bottom of the base piece in the channel or slot to attach the basepiece to a roof deck. A top piece can then be snapped into the slotafter installation of a photovoltaic element adjacent the base piece. Inthis alternative, mechanical fasteners beneath the photovoltaic elementscan be avoided. Of course, in alternative embodiments, the top piece caninclude the channel or slot, with the base piece having the featurewhich snaps into the channel or slot.

In another embodiment, the side flanges of the base piece include fabricnail hem as described for the attachment zone of siding panels in U.S.Pat. No. 5,857,303, which is hereby incorporated herein by reference inits entirety. This approach allows the use of staples as fastenersinstead of nails. In some cases this yields less vertical protrusion ofmechanical fasteners under photovoltaic elements than there may be withnail heads. In yet another alternative, the base piece is held in placeon the roof surface by an adhesive.

The photovoltaic roofing system can be used in conjunction with avariety of types of roofing elements. For example, in one embodiment theroofing elements are bituminous shingles. In other embodiments, theroofing elements are formed from slate, tile, composite, polymer, ormetal. Virtually any design of roofing element can be used in practicingthe present invention. For example, any suitable shingle shape can beused, including standard three-tab shingles as well as architecturalshingles of various thicknesses and designs. Various tile shapes, suchas flat tiles. “S”-shaped tiles and wavy tiles can be used.

The photovoltaic elements can be, for example, flexible photovoltaicelements, such as the flexible photovoltaic laminates sold by UnitedSolar Ovonic (Uni-Solar) under the product designation PVL (e.g.,PVL-68). PVL-68 laminates include a lengthwise extending plurality ofelectrically-interconnected photovoltaic cells. Of course, otherphotovoltaic elements can be used. In certain embodiments, thephotovoltaic elements can be wider, for example with an array havingmore than one cell along the width of the laminate, and a plurality ofcells extending along the length of the laminate. In one embodiment, thephotovoltaic elements are flexible photovoltaic elements that have agenerally strip-like shape (e.g., widths in the range of 0.3 m-0.7 m,and lengths of greater than 1 m), with the strips being oriented so thatthey run in a direction from the top edge of the photovoltaic area tothe bottom edge of the photovoltaic area. In certain embodiments, thephotovoltaic elements have at least one dimension greater than 1 m. Forexample, the photovoltaic element can have at least one dimensiongreater than 1 m, and another dimension greater than 0.5 m, 0.7 m, oreven 1 m. Wider laminates can reduce application time and reduce thenumber of standing seam flashings in the final system.

The photovoltaic elements can, in certain embodiments, have an adhesivelayer on their bottom surfaces (for example, accessible by removing aremovable release liner). The adhesive can adhere to the top surface ofthe roof deck (e.g., directly to the wood of the deck or to anunderlayment layer). One example of a possible underlayment material isan ice and water shield (e.g., a modified bituminous material such asWinterGuard® HT available from CertainTeed Corporation). Alternatively,a separate layer of a material can be disposed on the roof deck in thephotovoltaic area, and the adhesive layer can adhere to the material.The material can be, for example, a roofing membrane (e.g., formed fromthermoplastic polyolefin (TPO), PVC, EPDM, a bituminous material, or amodified bituminous material, e.g., WinterGuard® HT available fromCertainTeed Corp.), or an underlayment material (e.g., syntheticunderlayments, saturated underlayments). Moreover, the adhesive materialcan adhere to the flanges of flashing (both the side flashing and anyflashing disposed between contiguously-disposed photovoltaic elements inthe photovoltaic area. In some embodiments, it may be desirable to usean adhesion promoter to improve adhesion between any adhesive or sealantto the photovoltaic elements.

Another aspect of the invention is a kit for the installation of aphotovoltaic roofing system as described herein. The kit includes aplurality of base pieces as described herein; a plurality of top piecesas described herein. In another embodiment, the kit includes a pluralityof photovoltaic elements as described herein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the scope of the invention. Thus, it is intendedthat the present invention cover the modifications and variations ofthis invention provided they come within the scope of the appendedclaims and their equivalents.

1. A photovoltaic roofing system disposed on a roof deck, thephotovoltaic roofing system comprising: a two-part tee element disposedon the roof deck, the two-part tee element comprising: a base pieceincluding a central portion; two opposed horizontally-extending firstand second flanges extending from the central portion, and a top pieceattachment feature formed in the central portion, the top pieceattachment feature including an upwardly-extending feature, and a toppiece including a base piece attachment feature, the base pieceattachment feature including a downwardly-facing channel, the base pieceattachment feature being mated with the top piece attachment feature ofthe base piece by the upwardly-extending feature of the top pieceattachment feature of the base piece being disposed within thedownwardly-facing channel of the base piece attachment feature of thetop piece; a first covering flange extending outwardly from a side ofthe top piece, and a vertically extending portion extending upwards fromthe base piece attachment feature and the first covering flange; and afirst photovoltaic element disposed on the roof adjacent the base piece,the first photovoltaic element having its edge disposed on thehorizontally-extending first flange of the base piece of the two-parttee element, the first covering flange of the top piece overlapping thetop surface of the first photovoltaic element.
 2. The photovoltaicroofing system according to claim 1, wherein the first photovoltaicelement overlaps the first flange by at least about one inch.
 3. Thephotovoltaic roofing system according to claim 1, further including asecond photovoltaic element disposed on the roof adjacent the base pieceopposite the first photovoltaic element, the second photovoltaic elementhaving its edge disposed on the horizontally-extending second flange ofthe base piece of the two-part tee element.
 4. The photovoltaic roofingsystem according to claim 3, wherein the second photovoltaic elementoverlaps the first flange by at least about one inch.
 5. Thephotovoltaic roofing system according to claim 1, further including aroofing element disposed on the roof adjacent the base piece oppositethe first photovoltaic element, the roofing element having its edgedisposed on the horizontally-extending second flange of the base pieceof the two-part tee element.
 6. The photovoltaic roofing systemaccording to claim 5, wherein the roofing element overlaps the firstflange by at least about one inch.
 7. (canceled)
 8. The photovoltaicroofing system according to claim 1, further comprising a secondcovering flange extending outwardly from a side of the top pieceopposite the side from which the first covering flange extends, andoverlapping the top surface of a second photovoltaic element or aroofing element disposed on the roof adjacent the base piece, the firstphotovoltaic element or the roofing element having its edge disposed onthe horizontally-extending first flange of the base piece of thetwo-part tee element. 9-10. (canceled)
 11. The photovoltaic roofingsystem according to claim 1, wherein the material of the central portionof the base piece has a different material composition than do thematerials of the first and second flanges.
 12. The photovoltaic roofingsystem according to claim 11, wherein the first and second flanges areformed from a different material than is the base piece, and wherein thematerials of the first and second flanges are softer than the materialof the central portion of the base piece.
 13. The photovoltaic roofingsystem according to claim 1, wherein the top piece of the two-part teeis formed from a different material than the base piece.
 14. Thephotovoltaic roofing system according to claim 1, wherein when the basepiece attachment feature of the top piece is mated with the top pieceattachment feature of the base piece, the base piece attachment featureof the top piece is slidably engaged with the top piece attachmentfeature of the base piece, such that the top piece can slide withrespect to the base piece along the axis of the base piece.
 15. Thephotovoltaic roofing system according to claim 14, further comprising anend cap disposed at the bottom end of the base piece on the roof, theend cap engaging the base and closing the bottom end of the two-piecetee element.
 16. A method for installing a photovoltaic roofing systemaccording to claim 1 on a roof, the method comprising: affixing aplurality of base pieces to a roof, each base piece including a centralportion; two opposed horizontally-extending first and second flangesextending from the central portion, and a top piece attachment featureformed in the central portion, the top piece attachment featureincluding an upwardly-extending feature; disposing one or morephotovoltaic elements on the roof, each between two base pieces, suchthat each horizontal edge of each of the photovoltaic elements isdisposed on a flange of one of the base pieces; and assembling a toppiece with each base piece to form the two-part tee elements, each toppiece including a base piece attachment feature, the base pieceattachment feature including a downwardly-facing channel, the base pieceattachment feature being mated with the top piece attachment feature ofthe base piece by the upwardly-extending feature of the top pieceattachment feature of the base piece being disposed within thedownwardly-facing channel of the base piece attachment feature of thetop piece; a first covering flange extending outwardly from a side ofthe top piece, and a vertically extending portion extending upwards fromthe base piece attachment feature and the first covering flange. 17.(canceled)
 18. A kit for the installation of a photovoltaic roofingsystem according to claim 1, the kit comprising a plurality of basepieces, each base piece including a central portion; two opposedhorizontally-extending first and second flanges extending from thecentral portion, and a top piece attachment feature formed in thecentral portion, the top piece attachment feature including anupwardly-extending feature, and a plurality of top pieces, each toppiece including a base piece attachment feature, the base pieceattachment feature including a downwardly-facing channel, the base pieceattachment feature being adapted to be mated with the top pieceattachment feature of the base piece by the upwardly-extending featureof the top piece attachment feature of the base piece being disposedwithin the downwardly-facing channel of the base piece attachmentfeature of the top piece; a first covering flange extending outwardlyfrom a side of the top piece, and a vertically extending portionextending upwards from the base piece attachment feature and the firstcovering flange.
 19. The kit according to claim 18, further comprising aplurality of photovoltaic elements.
 20. The photovoltaic roofing systemaccording to claim 1, wherein the first covering flange of the top pieceis formed from a different material than the central portion of the toppiece, and wherein the first covering flange is formed from a rubbery orflexible material.
 21. The photovoltaic roofing system according toclaim 1, wherein the first covering flange of the top piece is formedfrom a different material than the central portion of the top piece, andwherein the first covering flange is formed from stiffer material thanthe central portion of the top piece.
 22. The photovoltaic roofingsystem according to claim 1, wherein the first photovoltaic element is aflexible photovoltaic laminate.
 23. The photovoltaic roofing systemaccording to claim 1, wherein the upwardly-extending feature of the toppiece attachment feature of the base piece is an upwardly-pointingtriangular feature, and wherein the downwardly-facing channel of thebase piece attachment feature of the top piece is a triangular channel.24. The photovoltaic roofing system according to claim 1, wherein thefirst covering flange of each top piece extends outwardly anddownwardly.
 25. The photovoltaic roofing system according to claim 8,wherein the second covering flange of each top piece extends outwardlyand downwardly.